Integrated circuit comprising supply polarity independent current injector

ABSTRACT

Integrated circuit suitable for any desired supply polarity by means of a rectifier bridge two rectifiers of which are designed as current injectors.

The invention relates to an integrated circuit comprising asemiconductor body and means for automatically ensuring the propersupply polarity, which means comprise two rectifiers having the samepass direction which are connected between a carrier zone of thesemiconductor element and two supply terminals.

In a known integrated circuit of this type the said rectifiers shunt themain current paths of two transistor amplifiers in a manner such that onapplication of one supply polarity one amplifier is rendered operativebecause the associated rectifier is cut off, whereas the other amplifieris short-circuited by its associated rectifier.

The object of the present invention is not at all to duplicate amplifierstages but to ensure in a simple manner that a supply current of theappropriate polarity reaches amplifiers or other circuit elements on thesemiconductor body.

The invention is characterized in that the said rectifiers form part ofa rectifier bridge whose pn junctions which, are formed with the carrierzone and are included in two other bridge arms, form part of a currentinjector for supply current to further circuit elements of theintegrated circuit. The invention is related to an invention withrespect to current injectors which is described in our co-pending DutchPat. application No. 7,107,040 (PHN 5,476). In contradistinction to thisprior proposal the present invention relates to two current injectorstructures, the injecting zone of one structure being polarized in theforward direction and that of the other in the reverse direction withrespect to the substrate zone, the carrier zone itself being connectedto the supply terminals not directly but via the aforementionedrectifiers.

It is known to provide a correct supply polarity by means of a rectifierbridge comprising four rectifiers. The invention utilizes therecognition that the two other rectifiers of this bridge may be providedso as to be capable of acting as current injectors. The term "currentinjector" is used herein to mean a multilayer structure having at leastthree successive layers, or regions, which are separated from each otherby rectifying junctions, which layers include a first layer, referred toas injecting layer, which is separated from the circuit element to besupplied with current by at least one rectifying junction, and anadjoining second layer consisting of a semiconductor material, which isreferred to as intermediate layer, the injecting layer being connectedto a supply terminal, whilst charge carriers are injected from theinjecting layer into the intermediate layer and are collected by thethird layer of the current injector, referred to as collecting layer,which adjoins the intermediate layer, a zone of one of the circuitelements to be supplied with current, referred to as zone to be biassed,which is separated from the injecting layer and hence from the supplyterminal connected thereto, by at least two rectifying junctions,collects, across a rectifying junction bounding this zone, chargecarriers from one of the layers of the current injector and thus issupplied with current, the said zone being directly connected to thepattern of metallic interconnections.

Embodiments of the invention will now be described, by way of example,with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 is a layout of the structure of a semiconductor body according tothe invention,

FIG. 2 is a side elevation thereof,

FIG. 3 is the equivalent circuit diagram of this structure,

FIG. 4 shows a modification of the left-hand part of the circuit diagramshown in FIG. 3, and

FIGS. 5, 6 and 7 are layouts of structures which correspond to thecircuit diagram of FIG. 4.

The semiconductor body shown in FIGS. 1 and 2 comprises a substrate ofn^(+-polarity) on which a weakly n-doped zone 4 is epitaxially grown. Inthis n-type zone 4, hereinafter referred to as carrier zone, verticalnpn transistors and lateral pnp transistors have been formed. A supplyterminal 1 is connected to an emitter 5 of a first npn verticaltransistor, the base 6 of which is connected by a metal interconnection3 to the carrier zone 4 which serves as the collector of the transistor5, 6, 4. Owing to this connection 3 the transistor 5, 6, 4 in knownmanner serves as a rectifier diode D₁, shown in FIG. 3. Similarly asupply terminal 2 is connected to an emitter 7 of a vertical npntransistor which has a base 6 and a collector 4 in common with thetransistor 5, 6, 4. Thus this second transistor 7, 6, 4 forms therectifier D₂ of FIG. 3. The supply terminals 1 and 2 are also connectedto p-type regions 9 and 10 respectively of lateral current injectors,the zones 9 and 10 serving as the injecting layers and the carrier zone4 serving as the intermediate layer, whilst a p-type collecting layer11, which surrounds the injecting layers 9 and 10 but is separatedtherefrom by the intermediate layer 4 and hence is not directlyconnected to a supply terminal, collects the injected charge carriersand transfers them to semiconductor elements to be supplied withcurrent.

This is effected in that the zone 11 -- hereinafter referred to asintermediate injector zone -- extends nearly to a large number ofsemiconductor elements which are to be supplied with current and onlytwo of which are shown in the form of vertical npn transistors formed inthe carrier zone 4. The carrier zone 4 serves as the emitter of thesevertical transistors, which in FIGS. 1 and 2 have their base zonesdenoted by 15 and 16 respectively and their collectors by 17 and 18respectively. Since the base zones 15 and 16 are close to the collectingzone 11 but are separated therefrom by the substrate zone 4, the chargecarriers collected by the zone 11 will partly reach the zones 15 and 16and so ensure the supply of current to the respective transistors.

In the equivalent circuit diagram of FIG. 3, the structure 9, 10, 4, 11is shown as a transistor T.sub. 3 having two emitters, which eachcorrespond to one of the zones 9 and 10, a common base, whichcorresponds to the zone 4, and a common collector, which corresponds tothe zone 11. The structures 4, 15, 17 and 4, 16, 18 correspond totransistors T₄ and T₅ respectively of the equivalent circuit diagram,and the structures 11, 4, 15 and 11, 4, 16 correspond to a transistor T₆of FIG. 3, the zone 11 serving as the emitter of the transistor T₆, thecarrier zone 4 as its base and the zones 15 and 16 as its collectors.The currents collected by the collectors of the transistor T₆ are usedto supply base current to the transistors T₄ and T₅ respectively, butalso indirectly to supply collector current to the transistor T₅ in thatthe base zone 15 of the structure 4, 15, 17, which corresponds to thetransistor T₄, is connected by a metal interconnection 19 to thecollector zone 18 of the structure 4, 16, 18 which corresponds to thetransistor T₅.

The structure shown requires a minimum number of masks and diffusionsteps and provides the large advantage that a wide variety ofsemiconductor elements of the integrated circuit may be supplied withcurrent without a separate metallic connection pattern to each of thesesemiconductor elements being required. Thus, in addition to leads 21 and22 between the supply terminal 1 and the zones 5 and 9 and between thesupply terminal 2 and the zones 7 and 10 respectively, only metalinterconnections between the semiconductor elements, one of which isshown by 19, are required. (These leads and interconnections are shownschematically in FIGS. 1 and 2, but in practice they will be provided asmetal conductors on an insulating film, for example an oxide film, onthe semiconductor body; if desired, in order to reduce the resistance ofthe intermediate injector zone 11 this zone may be coated at leastlocally by a metal conductor at areas at which this conductor does nothinder the aforementioned interconnection pattern).

The circuit described operates as follows:

When the semiconductor body is connected to the supply source, theterminal 1 being, for example, positive with respect to the terminal 2,current will flow from the terminal 1 through the lead 21, the pnjunction between the zones 9 and 4, which is polarized in the forwarddirection, the interconnection 3 and the pn junction between the zones 6and 7, which is operated in the forward direction, to the terminal 2. Asa result the carrier zone 4 assumes a potential which but for thevoltage drop across the diode D₂, i.e., the emitter base thresholdvoltage between the zones 7 and 6, is equal to the potential of theterminal 2. Because the zone 9 is polarized in the forward directionwith respect to the zone 7, charges will be injected from the zone 9into the zone 4 to be largely collected by the zone 11, because thiszone 11 entirely surrounds the zone 9. Thus the zone 11 assumes apotential nearly equal to that of the zone 9, i.e., that of theterminal 1. The ensuing current flowing to the zone 11 is evenly dividedbetween the further zones 15, 16 provided near the zone 11 and furtherp-type zones of circuit elements to be supplied with current. Theinjecting edge of the zone 11 is large with respect to the edge of eachof the collecting zones 15, 16 and with respect to those of the saidfurther p-type zones. In this respect the zone 10 will also collect partof the current from the zone 11, which consequently is to be consideredas a loss current, but because the collecting power of the zone 10 forcharges from the zone 11 is small compared with the collecting power ofthe zone 11 for charges from the zone 9, in other words because thecurrent gain of the transistor T₆ in the condition shown is considerablygreater than if the transistor T₆ were operated in the inversedirection, in which case the emitter and collector would beinterchanged, this loss current is negligible in practice.

When the polarity of the voltage at the supply terminals 1, 2 isreversed, the completely symmetrical construction will cause the zone 11to similarly continue to inject charge into the zones 15 and 16 to besupplied with current.

In order to reduce the voltage drop across the structure 7, 6, 4, i.e.,across the diode D₂, in the circuit shown in FIG. 2 the rectifiers D₁and D₂ are replaced by transistors T₁ and T₂ connected as rectifiers,either one or the other of these transistors being conducting. Thesetransistors have their emitters, which correspond to the zones 5 and 7respectively in FIGS. 1 and 2, connected to the supply terminals 1 and 2respectively, whilst their bases are connected via resistors R₁ andR.sub. 2 to current supply terminals 2 and 1 respectively, i.e., each tothe terminal other than that to which its emitter is connected. If now,for example, the terminal 1 is positive with respect to the terminal 2,the transistor T₁ will be cut off, whereas the transistor T₂ is renderedconducting via the resistor R₂ , but in this case the voltage differencebetween its emitter and collector, which correspond to the zones 7 and 4respectively in FIG. 1, now is equal only to the voltage drop across atransistor which is just not driven into saturation, which voltage dropin practice may be, for example, 0.1 volt, whereas in the configurationof the embodiment shown in FIGS. 1 and 2 it is about 0.6 volt. Theresistors are proportioned so that the base current of the transistor T₂still is small compared with its emitter collector current, but thevoltage between the base and the emitter has the same sign as (and isonly slightly greater than) the voltage between the base and thecollector.

In the layout shown in FIG. 5 the resistor R₁ and R₂ are formed asextensions 25 and 26 of the base zones 27 and 28 of the transistorstructures which correspond to 7, 6, 4 and 5, 6, 4 respectively. Theterminal 1 is connected by a lead 29 to the emitter 30 of one pnptransistor the collector of which in this structure also is formed bythe carrier zone 4 and by a lead 31 to a contact pad 32 on the baseresistor 25. Similarly the terminal 2 is connected by a lead 33 to theemitter 34 of the other pnp transistor and by a lead 35 to a contact pad36 on the base resistor 26. The zone 11, the function of which entirelycorresponds to that which it has in the layout shown in FIG. 1, isprovided with fingers 37, 38 and 39 which partly embrace the zones 25and 26.

Assuming the supply polarity to be such that the terminal 1 is positivewith respect to the terminal 2, there will be applied to the zone 25 viathe contact pad 32 a forward voltage which causes the base zone 27 to bepolarized in the forward direction with respect to the emitter zone 34,so that the structure 34, 27, 4 is rendered conductive and hence thesubstrate Zone 4 assumes substantially the potential of the terminal 2.On the other hand the zone 25, at least in the proximity of the contactpad 32, will emit a considerable amount of charges into the substratezone 4, which are collected by the fingers 37 and 38 of the zone 11. Atthe same time the transistor structure comprising the zones 30, 28 and 4is rendered non-conductive, inter alia owing to the small voltagedifference between the zones 4 and 28, so that substantially no currentflows in this structure.

The base resistor formed by the zone 26 will, at least in the proximityof the contact pad 36, collect current which is injected from thefingers 38 and 39 of the zone 11 into the substrate zone 4, and thiscurrent is again to be regarded as a loss current. To reduce thiscurrent the fingers 37, 38 and 39 preferably embrace the resistancezones 25 and 26 partly only, as is indicated by broken lines, for owingto the voltage drop across the resistance zone 25 the voltage differenceof this zone 25 relative to the substrate zone 4 will be greatest in theproximity of the contact pad 32, so that in this area the largestinjection into the zone 11 takes place. Consequently, shortening thefingers 37 and 38 does not greatly reduce the useful injection into thezone 11, but does reduce the loss current flowing from the fingers 38and 39 to the zone 26.

FIG. 6 shows another solution of this problem which enables these losscurrents to be further reduced. In this embodiment the base zones 27 and28 are expanded so as to enable them to contain resistance zones 42 and41 respectively which are in the form of (n-type) extended portions ofthe associate emitter zones 34 and 30 respectively. The terminal 1 herealso is connected to the n-type emitter zone 30 at the site of thecontact pad 43 and also to the p-type injection zone 9. Similarly theterminal 2 is connected to the n-type emitter zone 34 at the site of thecontact pad 44 and also to the p-type injector zone 10. The ends 45 and46 of the resistance zones 41 and 42 more remote from the contact pads43 and 44 respectively are connected to the base zones 27 and 28 viametal interconnections 27 and 48 respectively.

Assuming again that the terminal 1 has positive polarity with respect tothe terminal 2, current flowing via the contact pad 43, the resistancezone 41, the contact pad 45 and the metal interconnection 47 willpolarize the base zone 27 in the forward direction with respect to theemitter zone 34, so that the structure 34, 37, 4 becomes highlyconducting and the carrier zone 4 substantially assumes the potential ofthe terminal 2. Consequently the injector zone 9 will be polarized inthe forward direction with respect to the carrier zone 4, so thatcharges are injected, which are collected by the zone 11. However, theinclusion of the resistance zones 41 and 42 in the base zones 28 and 27respectively prevents these base zones from giving rise to undesirablecollector action. This is inter alia due to the fact that when thestructure 34, 27, 4, which corresponds to the transistor T₂ in FIG. 4,is in the highly conducting condition the inverse current conduction bythe transistor T₁, which corresponds to the structure 30, 28, 4, isprevented.

An additional effect is that the zone 6 in FIGS. 1 and 2 and the zones27 and 28 in FIGS. 5 and 6 can directly collect injection current fromthe zone 11. If this is regarded as an undesirable phenomenon, thesezones 6 or 27 and 28 are to be spaced by an appropriate distance fromthe zone 11, or another provision is to be made to ensure that thesecurrents are avoided, for example by the interposition of afinger-shaped p-type zone which may be connected to the carrier zone 4.As an alternative, however, this current may be turned to account, as isshown in FIG. 7, by locating the base zones 51 and 52 of thenpn-structures 5, 51, 4 and 7, 52, 4 respectively in the proximity ofthe zone 11, so that part of the current from the zone 11 is used torender the relevant transistor structure conductive. If, for example,the terminal 1 is again positive with respect to the terminal 2, thepn-junction 9, 4 and the pn-junction 52, 7 will be polarized in theforward direction. Thus, the four zones 9, 4, 52 and 7 form apnpn-structure which may become astable as a sufficient number of freecharges occur. These free charges are obtainable, for example, byconnecting resistors to suitably chosen points; the simplest manner ofproducing these free charges is to apply a short duration sufficientlyhigh start pulse between the supply terminals or to irradiate thesemiconductor element with radiation of sufficient intensity for a giventime. When in this manner charge injection from the injector zone 9 intothe carrier zone 4 has been started, charges will be collected by thezone 11 to be partly injected again into the zone 4 in the proximity ofthe zone 52, by which they are collected whereupon they will reach thesupply terminal 2 via the zone 7. The injection current from the zone 9will be substantially entirely collected by the zone 11; because thiszone 11, however, supplies current to a large number of circuit elements-- in the same manner as is indicated in FIGS. 1 and 2 -- only a smallportion of this current will reach the zone 52. There this current actsas the base current of the vertical transistor 7, 52, 4 and may be largeenough to maintain this transistor in its highly conducting condition.

In the examples described so far the injector zone 9 or 10 together withthe carrier zone 4 and the intermediate injector zone 11 forms a lateraltransistor. In principle the injector may also be designed as a verticaltransistor by starting from a p-type substrate instead of from then^(+-type) layer of FIG. 2, forming an epitaxial n-type layercorresponding to the carrier zone 4 of FIG. 2 on the substrate, and byforming in this epitaxial layer vertical transistor structures whichcorrespond to 15, 17 and 16, 18 of FIGS. 1 and 2, rectifier structureswhich correspond to 3, 4, 5, 6, 7 in FIGS. 1 and 2, and injectors whichcorrespond to zones 9 and 10 in FIGS. 1 and 2, which are similarlyconnected to the supply voltage terminals. (Thus the zone 11 of FIGS. 1and 2 is dispensed with). When a supply voltage is applied the rectifierstructures will similarly ensure that the n-type epitaxial substratezone assumes a potential nearly equal to that of the negative supplyterminal, whilst the current from the injector zone connected to thepositive supply terminal will reach, through the n-type epitaxialsubstrate zone, the p-type substrate and via the latter may serve tosupply current to the various transistor structures on the semiconductorbody. However, the advantage of this solution that the zone 11 isdispensed with is offset by the disadvantage that the operation of thesubstrate zone as a low-resistance supply current conductor and as anemitter for the structures corresponding to 15, 17 and 16, 18 of FIG. 1is performed with considerably less efficiency, because the favourableeffect of the n^(+-doped) substrate of FIG. 2 is absent.

Further steps described in the aforementioned copending PatentApplication of prior date may advantageously be applied to theaforedescribed embodiments. In particular the efficiency is considerablyincreased by surrounding the intermediate injector zone 11 and the zonesto be supplied with current by an isolating or n^(+-doped) zone (shownshaded in FIG. 1) which, if desired, may extend into the n^(+-doped)substrate and substantially prevents the injected charges from leakingaway. In FIG. 7 a similar step may be taken with respect to theintermediate injector zone 11 and the rectifier structures 5, 51, 4 and7, 52, 4.

Obviously all the dopings mentioned may be of the opposite types, inwhich case the voltage polarities also will be reversed. Furthermore, ifdesired, a supply alternating current may be applied to the terminals 1and 2; in this case the capacitance between the zones 4 and 11 ispreferably increased by providing these zones with contact pads betweenwhich a capacitor is connected.

What is claimed is:
 1. An integrated circuit comprising:a. asemiconductor body comprising semiconductor circuit elements and acarrier zone, b. means for supplying electrical potential to saidsemiconductor body, c. a rectifier bridge disposed at said semiconductorbody and comprising bridge arms, said bridge comprising two respectivefirst rectifier elements disposed in said carrier zone and .[.saidrectifier.]. included in respective first ones of said bridge arms toform part of said bridge, said rectifier elements being electricallyconnected between said potential supplying means and said carrier zone,d. further rectifier elements disposed in second ones of said bridgearms, and e. means for automatically ensuring the appropriate supplycurrent polarity to said semiconductor elements, said means comprisingcurrent injector elements respectively disposed in said second bridgearms and being in current supply relationship with said circuitelements.
 2. An integrated circuit as claimed in claim 1, wherein saidcurrent injector elements comprise lateral transistors.
 3. An integratedcircuit as claimed in claim 1, wherein said circuit elements comprisecircuit zones for receiving current from respective said currentinjector elements and said current injector elements comprise a zonehaving an edge area substantially larger than that of each of saidcircuit element zones.
 4. An integrated circuit as claimed in claim 1,wherein said first rectifiers comprise vertical transistors disposed insaid carrier zone and that respectively comprise collector regions,emitter regions that are connected to said potential supply means.Iadd.and base regions that are cross-connected to said supply means.Iaddend.through resistors.
 5. An integrated circuit as claimed in claim4, wherein said resistors comprise extensions of said base zones of saidvertical transistors provided in said carrier zone.
 6. An integratedcircuit as claimed in claim 5, wherein said extensions further comprisea part of said current injector elements.
 7. An integrated circuit asclaimed in claim 5, wherein said resistors comprise extensions of saidemitter zones of said vertical transistors, said extensions projectinginto said base zones.
 8. An integrated circuit as claimed in claim 1,wherein said first rectifiers comprise vertical transistors provided insaid carrier zone and disposed proximity to said current injectorelements so as to be supplied with the required base currents thereby.9. An integrated circuit as claimed in claim 1, wherein said currentinjector element and the zones of said circuit elements to be suppliedwith current are laterally surrounded by a highly doped zone, so as toprevent injection currents from leaking away.
 10. An integrated circuitas claimed in claim 1 suitable for alternating-current supply, wherein acapacitor element is connected between an injecting zone of the currentinjector element and the carrier zone. .Iadd.
 11. An integrated circuit,comprising:a. at least one circuit element; b. bias supply terminals forbiasing said circuit element; and c. means for automatically ensuringthe appropriate polarity bias to said circuit element, said meanscomprising a bridge rectifier circuit electrically connected to saidterminals and that comprises in each of two arms thereof a currentinjector coupled to said bias receiving circuit element, said currentinjectors comprising respective rectifying junctions, which, uponforward biasing, can inject carriers from a region outside said circuitelement and cause collection of carriers by an active zone of saidcircuit element so as to bias said circuit element. .Iaddend..Iadd. 12.An integrated circuit as in claim 11, wherein said bridge rectifiercircuit further comprises first rectifiers in respective other armsthereof. .Iaddend..Iadd.
 13. An integrated circuit as in claim 12,wherein said first rectifiers comprise respective vertical n,p,n,transistor structures and each of said current injectors comprises alateral pnp, transistor, said vertical transistor structures havingtheir respective base regions electrically connected to their respectivecollector regions. .Iaddend. .Iadd.
 14. An integrated circuit as inclaim 13, wherein said integrated circuit comprises a semiconductor bodycomprising a carrier zone that forms part of said rectifying junctionand that comprises said collector regions of said vertical transistorstructures..Iaddend..Iadd.
 15. An integrated circuit as in claim 13,wherein said vertical transistor structures have common base regions andcommon collector regions. .Iaddend..Iadd.
 16. An integrated circuit asin claim 13, wherein said supply terminals are connected to respectiveemitter regions of said vertical transistor structures and to respectiveemitter regions of said lateral transistors. .Iaddend..Iadd.
 17. Anintegrated circuit as in claim 13, wherein each said supply terminal isconnected to a respective said emitter region of said verticaltransistor structures and cross-connected through a resistor to arespective said base region of said vertical transistor. .Iaddend..Iadd.18. An integrated circuit as in claim 11, wherein each of said currentinjectors comprises at least three successive regions separated fromeach other by rectifying junctions, said regions respectivelyconstituting an injecting region that is separated from said circuitelement by at least one rectifying junction, an intermediate regionadjoining said injecting region and a collecting region adjoining saidintermediate region. .Iaddend. .Iadd.
 19. An integrated circuit as inclaim 18, wherein said collecting region comprises said active zone ofsaid circuit element, said active zone being separated from saidinjecting region by at least two rectifying junctions and being biasedby said supplied current. .Iaddend..Iadd.
 20. An integrated circuit asin claim 18, wherein said collecting region comprises an intermediateinjector zone disposed between said injecting region and said zone ofsaid further circuit element. .Iaddend..Iadd.
 21. An integrated circuitas in claim 18, wherein said collecting region forms a collector zone ofa first transistor and an emitter zone of a second transistor, whereinsaid active zone comprises the collector zone of said second transistor..Iaddend..Iadd.
 22. An integrated circuit comprising a circuit element arectifier bridge that comprises plural rectifiers included in respectivearms of said bridge, a number of said rectifiers comprising currentinjector means for supplying current to a circuit element and biasing azone of said element so that said element is rendered conductive..Iaddend..Iadd.
 23. An integrated circuit comprising: a. a circuitelement; b. a semiconductor element comprising a carrier zone; c. pluralsupply terminals; d. means for ensuring the appropriate supply polarityto said circuit element, said means comprising a rectifier bridge thatincludes plural rectifiers electrically connected between said carrierzone and respective said supply terminals and located in respective armsof said bridge; and e. said rectifier bridge further comprising p,njunctions formed with said carrier zone and located in respective otherbridge arms, said p,n junctions comprising a current injector forsupplying current to said further circuit element. .Iaddend..Iadd. 24.An integrated circuit as in claim 17, wherein said resistors compriseextensions of said vertical transistor emitter regions which formislands within said vertical transistor base regions. .Iaddend.